This invention relates to a novel wheelchair device. The wheelchair of this invention is particularly, although not exclusively, adapted for recreational purposes, including applications allowing the user to be transported across soft uneven surfaces such as a sandy beach or muddy lake shore and further to be transported into water of limited depths. The construction of this wheelchair is particularly adapted for these purposes utilizing corrosion resistant materials and wheel structures adapted to travel over soft, uneven surfaces.
At present, most wheelchairs are designed to transport occupants across paved surfaces such as hospital hallways or other indoor environments. As a result, these chairs are designed with low friction bearings and large diameter, thin tubular rim wheels to offer the least resistance when transporting an occupant across such surfaces. The chairs are constructed of high quality, high strength stainless steel or other similar materials. Such wheelchairs typically cost in the range of $3,000 to $5,000 and are intended to have useful lifetimes on the order of ten years. In addition, conventional wheelchairs are provided with elaborate mechanisms to allow for folding and collapsing of the wheelchair for transportation and storage. These elaborate mechanisms are subject to corrosion when exposed to outdoor environments and must be maintained diligently to avoid rusting and deterioration of moving parts.
The front wheels of conventional wheelchairs typically take the form of small casters which may swivel about a vertical axis to permit ease of steering and self-propulsion of the chair by the occupant. Such wheels are of small diameter and narrow width to facilitate swiveling.
Because of the high quality bearings and materials that are utilized in conventional wheelchairs, they have been, in general, unacceptable for use in outdoor applications. Specifically, the corrosive nature of outdoor elements such as seawater, sand, solar radiation and debris found in recreational environments make prior wheelchair designs unacceptable. The materials chosen are not suited for long term exposure to sun and sand, etc.. Further, the narrow tires used on conventional wheelchairs to reduce rolling resistance do not permit travel over soft surfaces such as sand, mud, or uneven terrain. It is an object of the present invention to provide an ambulatory vehicle or wheelchair which overcomes these and other limitations of prior devices.
Conventional wheelchairs have at times in the past been constructed of non-metallic materials to avoid causing interference in instruments such as nuclear magnetic resonance imaging devices. Such wheelchairs are represented in U.S. Pat. No. 4,770,432 to Wagner wherein is disclosed a conventional wheelchair partially constructed of non-metallic materials. Such wheelchairs are of completely conventional design but for the choice of construction materials and thus retain the disadvantages of conventional wheelchairs with regard to recreational activities.
The tire construction utilized in Wagner, for example, prevents use on uneven or soft surfaces. In addition, the non-metallic materials chosen appear to be custom molded of rigid skinned polyurethane. The wheelchair parts are affixed utilizing nonmagnetic metals. The intricate mechanisms of Wagner are inappropriate for marine environments.
A prior art device directed toward providing a wheelchair for travel over uneven surfaces is disclosed in Randolph, U.S. Pat. 4,077,483. The Randolph device consists of a conventional wheelchair seat which has been provided a tank-like tractor arrangement rather than wheels. The device is further provided with an electric motor and control mechanism to allow the occupant to direct the chair. The device does not, however, accommodate soft surfaces such as dry sand or estuary shores and instead is directed toward inclined on stepped surfaces such as floors, sidewalks or entering or exiting a vehicle.
One example of a prior art attempt to produce a wheelchair suitable for use and recreational contexts is disclosed in Rice et. al., U.S. Pat. No. Des. 294,811. The Rice disclosure sets forth a basic wheelchair design having two oversized rear wheels of exaggerated thickness much like wagon wheels. The wheelchair shown in Rice is an attempt to provide rear wheels which have some capability for travelling over soft or uneven surfaces. The front wheels of the Rice wheelchair had been removed and instead have been replaced with simple post supports. The lack of front wheels in the Rice design renders it ineffective for use with invalids of significant weight or incapacity. The Rice design must be moved in an inclined position at all times rendering it difficult to manage for the attendant.
A still further example of prior art devices which attempts to provide a wheelchair in recreational contexts is set forth in the French Patent document No. 2,423,212 issued to Escande. The Escande device discloses a conventional wheelchair provided with larger rear tires. The Escande device suffers from the lack of any provision of soft terrain means in the front of the device. This device must be moved over soft terrain in an inclined position producing difficulty for both chair occupant and attendant.
As will be understood, the wheelchair of this invention overcomes many of the disadvantages of prior art. The difficulties and limitations suggested in the preceding are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness and user satisfaction with prior recreational wheelchairs and the like. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that prior recreational wheelchairs appearing in the past will admit to worthwhile improvement.